Methods for Introducing Pulsing to Cementing Operations

ABSTRACT

A method for bonding a well bore to a casing may include several steps. Casing may be introduced into the well bore and pulses of fluid may be directed from within the casing into the well bore. An annulus between an inner surface of the well bore and an outer surface of the casing may be filled with fluid. A method for reducing fluid or gas migration into a fluid in the annulus may include inducing pressure pulses in the fluid before the fluid has cured.

BACKGROUND

The present invention relates to cementing operations, and, moreparticularly, methods and apparatuses for providing more competentcement bonds during and after cementing operations in well bores.

Settable compositions such as cement slurries may be used in primarycementing operations in which pipe strings, such as casing and liners,are cemented in well bores. In performing primary cementing, a cementmay be pumped through the casing into an annulus between the walls of awell bore and the casing disposed therein. The cement typically ispumped into this annulus until it reaches a predetermined height in thewell bore to provide zonal isolation. The cement cures in the annulus,thereby forming an annular sheath of hardened cement (e.g. a cementsheath) that supports and positions the pipe string in the well bore andbonds the exterior surface of the pipe string to the walls of the wellbore.

Fluid or gas influx into the annulus and cement therein during thecement curing or “gelling” stage is quite common. This fluid or gasinflux can damage the cement bond between the well bore formation andthe exterior surface of the casing. Moreover, the buildup of residuessuch as filter cake on or in the surface of the well bore also canprevent a complete bond between the cement and the well bore. FIG. 1illustrates an example of such damage and incomplete bonding in a smallsection of formation 100 containing well bore 101 with casing 102.Cement 103 fills annulus 104 between the walls of well bore 101 and theexterior surface of casing 102. Pockets 105 and 106 illustrate examplesof damage caused by fluid or gas influx. If the fluid or gas invasion issevere, channels will form between formation 100 and the exteriorsurface of casing 102, such as channels 107 and 108. Influx damage canoccur at the interface between cement 103 and well bore 100, or in thecement 103 itself. Filter cake 109 also can prevent complete bondingbetween well bore 101 and cement 103. Conventional methods of filtercake removal often rely on mechanical means such as scratchers with pipereciprocation or require that cement 103 reach a specific annularvelocity. These removal methods can be time-consuming and often leavefilter cake residues behind, impeding bonding between cement 103 andwell bore 101.

SUMMARY

The present invention relates to cementing operations, and, moreparticularly, methods and apparatuses for providing more competentcement bonds during and after cementing operations in well bores.

A method for bonding a well bore to a casing therein, may comprise thesteps of introducing the casing into the well bore, directing pulses offluid from within the casing into the well bore, and filling an annulusbetween an inner surface of the well bore and an outer surface of thecasing with the fluid. The step of directing pulses of fluid mayperformed while moving the casing further into the well bore.Additionally or alternatively, the method may further comprise the stepof selecting a frequency and pressure level for the pulses of fluid soas to reduce filter cake formed on the inner surface of the well bore.Additionally or alternatively, the method may further comprise the stepof vibrating well fluid at a resonance frequency for the well fluid.Additionally or alternatively, the method may further comprise the stepof vibrating the casing at a resonance frequency for the casing.Vibrating the casing at a resonance frequency may comprise the step ofdirecting pulses of fluid into the well bore at a frequency and pressureselected to induce resonance vibrations in the casing. Additionally, oralternatively, the fluid may be a cement. If the fluid is a cement, themethod may further comprise the step of selecting a frequency andpressure level for the pulses of fluid so as to reduce the amountnon-cement material on the casing, and the method may further comprisethe step of selecting a frequency and pressure level for the pulses offluid so as to reduce filter cake formed on the inner surface of thewell bore, such that the pulses have a dual-step profile.

A method for reducing fluid or gas migration into a fluid in an annulusformed between a surface of a well bore in a formation and a casing, maycomprising the step of inducing pressure pulses in the fluid before thefluid has cured. The fluid may be a cement. The method may furthercomprise the step of selecting a frequency and amplitude for thepressure pulses such that the pressure pulses prevent shear damage ofthe fluid during curing. The step of inducing pressure pulses in fluidbefore the fluid has cured may comprise the step of inducing alow-amplitude pressure pulse. Additionally, or alternatively, the stepof inducing pressure pulses in fluid before the fluid has cured maycomprise the step of inducing a low-frequency pressure pulse.Alternatively, the step of inducing pressure pulses in fluid before thecement has cured may comprise the step of inducing a pressure pulsehaving a dual-step profile.

The features and advantages of the present invention will be readilyapparent to those skilled in the art. While numerous changes may be madeby those skilled in the art, such changes are within the spirit of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

These drawings illustrate certain aspects of some of the embodiments ofthe present invention, and should not be used to limit or define theinvention.

FIG. 1 illustrates conventional cement bonding.

FIG. 2 illustrates a method for bonding a well bore to a casing inaccordance with one embodiment of the present invention.

FIG. 3 illustrates an alternate embodiment of a method for bonding awell bore to a casing.

FIG. 4 illustrates yet another embodiment of a method for bonding a wellbore to a casing.

FIG. 5 illustrates various pressure pulses in accordance with oneembodiment of the present invention.

FIG. 6 illustrates a shear damage profile in accordance with oneembodiment of the present invention.

FIG. 7 illustrates a fluidic oscillator in accordance with oneembodiment of the present invention.

FIG. 8 illustrates an alternate embodiment of a method for bonding awell bore to a casing.

FIG. 9 illustrates yet another embodiment of a method for bonding a wellbore to a casing.

DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention relates to cementing operations, and, moreparticularly, methods and apparatuses for providing more competentcement bonds during and after cementing operations in well bores.

These methods and apparatuses may result in less fluid influx during thepre and post gelling stage of a cement slurry or other fluid, resultingin significant savings in time and cost, and improved hydrocarbonrecovery.

Typically, a cementing operation involves attaching float shoe 110 to anend of casing 102 and introducing casing 102 into well bore 101. Cement103 may then flow down the interior of casing 102 and out through floatshoe 110 into annulus 104. Alternatively, a reverse cementing operationmay be used to place cement 103 in annulus 104. In either instance, ascement 103 enters annulus 104, it displaces material such as drillingfluid, filter cake, gas, or debris occupying annulus 104. Typically, ascement 103 enters annulus 104, some material occupying annulus 104remains, particularly near the walls of well bore 101 and casing 102. Inother words, a displacement efficiency of the material is typicallysignificantly below 100% efficiency, which would correspond to theinstance when cement 103 completely displaces the material occupyingannulus 104. Low displacement efficiency results in undesirablechanneling and pocketing, which causes the cement bond to becompromised.

The material may be more completely replaced by cement 103 when pulsingor oscillation is used during the introduction of cement 103 intoannulus 104. A number of devices rely on fluid oscillation effects tocreate pulsating fluid flow. Generally, these devices connect to asource of fluid flow, provide a mechanism for oscillating the fluid flowbetween two different locations within the device and emit fluid pulsesdownstream of the source of fluid flow. These “fluidic oscillator” 112devices require no moving parts to generate the oscillations and havebeen used in various applications for which pulsating fluid flow isdesired, such as massaging showerheads, flow meters, andwindshield-wiper-fluid-supply units. Specialized fluidic oscillatordevices have been developed for the oilfield industry, such as, forexample, the Pulsonix TF tool offered by Halliburton Energy Services,Inc. of Duncan, Okla.

In addition to providing for more complete displacement of materials inannulus 104, fluidic oscillator 112 may help mitigate fluid and/or gasmigration during cement cure time. As shown in FIG. 2, fluidicoscillator 112 may be present in float shoe 110. In this embodiment, afeedback loop may be scaled and adapted to allow desired flow rates andcement passages to allow application into a Super Seal II float shoe bymatching flow areas of the 2¾″′ or 4¼″ Super Seal II Valves. This mayallow for filter cake 109 removal while running in hole using a topdrive unit. Filter cake 109 may be removed more effectively by directfluid impingement of the well bore 101. Once total depth (“TD”) isreached reduced well conditioning time (bottoms up) may be required,since filter cake may be removed hydraulically while running in hole,instead of requiring cleaning at a specific annular velocity or bymechanical means such as scratchers and pipe reciprocation. Pulsing maybreak down gel strength, fragmenting or breaking down filter cake 109.

Referring now to FIG. 3, an additional benefit of fluidic oscillator 112in float shoe 110 may be available in either standard or top driveapplications. As a result of the oscillatory effect at float shoe 110,cement 103 is displaced more effectively at the walls of well bore 101and casing 102. The oscillation effect tends to place cement 103 furtherinto formation 100, compacting cement 103, which results in fewer voidsdue to filter cake contamination entrapment or consistency issues.Another potential advantage is that casing 102 may be set into resonanceby the oscillation at float shoe 110. This resonance tends to preventvoids at the wall of casing 102. The resonance and compaction effectcontinuously occurs from the beginning of the displacement until the topplug lands or pumping is discontinued. Alternatively, or additionally,frequency may be set such that the well bore fluids are set intoresonance.

Since each well will have different frequency variables, such as fluid,rate, and geometry, it may be particularly useful for fluidic oscillator112 to have variable components. A fluctuating or variable fluidicoscillator 112 may be used to allow for alternating resonance of casing102 and well bore fluids. A high frequency component, a low frequencycomponent, or a combination of the two may enhance the effectiveness ofthe system. These components may be further combined with either high orlow amplitude components, or both. To reach the various resonanceranges, variable rate or “dual-step profile” pumping may be used.Alternatively, two or more fluidic oscillators 112 could be used toalternate between two or more resonances.

As an alternative to alternating between multiple frequencies and/oramplitudes, a specific design may be used for a specific well bore fluidsystem. As more cement 103 is pumped, resonant frequency will change.Thus it may be desirable for fluidic oscillator 112 to change based onchanges in the system. This may be a result of monitoring ofinstrumentation measuring the level of excitation. This may be done witha sensor such as a hydrophone, a pressure transducer, a flow device, anaccelerometer, or any number of other devices known in the art. Thismonitoring may allow for fluidic oscillator 112 to maintain resonance.

Referring now to FIG. 4, in an alternative embodiment, low frequency,low pressure pulses are induced after the plug has landed and the curinghas begun. A pressure pulsation tool 114 may be optimized from itsnormal high amplitude/low frequency configuration to a low amplitude/lowfrequency tool by way of configurable inserts and pump rate control.Pressure pulsation tool 114 may be encapsulated in a canister and usedin conjunction with a reservoir system to create a surface cementpulsation system to apply low pressure/low frequency pressure pulses toannulus 104 to delay the curing time and prevent fluid migration as aresult of cement volume reduction.

Idealized pressure wave forms can be controlled to provide optimalpulsation and help prevent shear of cement 103 during dehydration.Examples of what the inventors envision as optimal pressure pulses areillustrated in FIG. 5. These profiles may prevent shear damage to cement103, as indicated in FIG. 6.

Yet another embodiment involves a low cost “tubing” size fluidicoscillator 112, as shown in FIG. 7. This fluidic oscillator 112 may becomposed of phenolic inserts cemented into a low cost case. Cement 103may be fairly resistant to acid, thus allowing application to hydraulicwork order (“HWO”) or Well Intervention applications in addition tocementing applications.

The concept of “pulsing” the top plug after catching cement isillustrated in FIG. 8. A pulse generator capable of pumping cement mayallow for pulsing on the fly or, as illustrated, pulsing of thedisplacement fluid could be accomplished.

Pulsation or oscillation may be used to set more competent balancedplugs. Shown in FIG. 9 is an oscillation guide shoe 113 used with eitherthe tubing release tool (“TRT”) or bottom hole kickoff assembly (“BHKA”)tool. Retrieving drillpipe adapter and collet retainer 115 may beremoved as releasing plug 116 is latched and collet is disengaged,releasing tubing. Alternatively, pressure pulsation may be used duringhesitant squeeze cementing (not shown).

This disclosure covers two basic fluid energy principles: fluidicoscillation and pressure pulsing technology. These two principles can beused during or after the cementing job. This technology is adaptable forboth primary cementing and setting of balanced plugs.

This technology potentially could reduce sustained casing pressure whichis a major concern particularly offshore. Earlier methods do notconsider the advantage of inducing fluid energies by fluidic oscillationor pressure pulsation methods. This methodology greatly enhances thechances for competent cement bonding.

Therefore, the present invention is well adapted to attain the ends andadvantages mentioned as well as those that are inherent therein. Theparticular embodiments disclosed above are illustrative only, as thepresent invention may be modified and practiced in different butequivalent manners apparent to those skilled in the art having thebenefit of the teachings herein. Furthermore, no limitations areintended to the details of construction or design herein shown, otherthan as described in the claims below. It is therefore evident that theparticular illustrative embodiments disclosed above may be altered ormodified and all such variations are considered within the scope andspirit of the present invention. In particular, every range of values(of the form, “from about a to about b,” or, equivalently, “fromapproximately a to b,” or, equivalently, “from approximately a-b”)disclosed herein is to be understood as referring to the power set (theset of all subsets) of the respective range of values, and set forthevery range encompassed within the broader range of values. Also, theterms in the claims have their plain, ordinary meaning unless otherwiseexplicitly and clearly defined by the patentee.

1. A method for bonding a well bore to a casing therein, comprising thesteps of: introducing the casing into the well bore; directing pulses offluid from within the casing into the well bore; and filling an annulusbetween an inner surface of the well bore and an outer surface of thecasing with the fluid.
 2. The method of claim 1, wherein the fluid is acement.
 3. The method of claim 1, wherein the step of directing pulsesof fluid is performed while moving the casing further into the wellbore.
 4. The method of claim 1, further comprising the step of selectinga frequency and pressure level for the pulses of fluid so as to reducefilter cake formed on the inner surface of the well bore.
 5. The methodof claim 2, further comprising the step of selecting a frequency andpressure level for the pulses of fluid so as to reduce the amountnon-cement material on the casing.
 6. The method of claim 5, furthercomprising the step of selecting a frequency and pressure level for thepulses of fluid so as to reduce filter cake formed on the inner surfaceof the well bore, such that the pulses have a dual-step profile.
 7. Themethod of claim 1, further comprising the step of vibrating the casingat a resonance frequency for the casing.
 8. The method of claim 7,wherein the step of vibrating the casing at a resonance frequencycomprises the step of directing pulses of fluid into the well bore at afrequency and pressure selected to induce resonance vibrations in thecasing.
 9. The method of claim 1, further comprising the step ofvibrating well fluid at a resonance frequency for the well fluid. 10.(canceled)
 11. (canceled)
 12. A method for reducing fluid or gasmigration into a fluid in an annulus formed between a surface of a wellbore in a formation and a casing, comprising the step of inducingpressure pulses in the fluid before the fluid has cured, furthercomprising the step of selecting a frequency and amplitude for thepressure pulses such that the pressure pulses prevent shear damage ofthe fluid during curing.
 13. The method of claim 12, wherein the step ofinducing pressure pulses in fluid before the fluid has cured comprisesthe step of inducing a low-amplitude pressure pulse.
 14. The method ofclaim 12, wherein the step of inducing pressure pulses in fluid beforethe fluid has cured comprises the step of inducing a low-frequencypressure pulse.
 15. A method for reducing fluid or gas migration into afluid in an annulus formed between a surface of a well bore in aformation and a casing, comprising the step of inducing pressure pulsesin the fluid before the fluid has cured, wherein the step of inducingpressure pulses in fluid before the cement has cured comprises the stepof inducing a pressure pulse having a dual-step profile.